Heat exchangers



June 19, 1962 H. JACOBS El'AL 3,039,744

HEAT EXCHANGERS Filed Sept. 1, 1955 4 Sheets-Sheet 1 FIG.I

INVENTORS F165 HEINZ JACOBS JOHANNES GLAESGENS FRIEDBERT HEYN ATTORNEY June 19, 1962 Filed Sept. 1 1955 H. JACOBS ETAL HEAT EXCHANGERS 4 Sheets-Sheet 2 FIG.8

INVENTORS HEINZ JACOBS JOHANNES CLAESGENS FRIEDBERT HEYN ATTORN EY June 19, 1962 JACOBS ETAL 3,039,744

HEAT EXCHANGERS Filed Sept. 1 1955 4 SheetSSheet 3 INVENTORS HEINZ JACOBS JOHANNES CLAESGENS FRIEDBERT HEYN ATTORNEY June 19, 1962 FIG.6

INV ENTORS HEINZ JACOBS JOHANNES GLAESGENS FRIEDBERT HEYN ATTORNEY United States Patent Oflflce 3,039,744 Patented June 19, 1962 3,039,744 HEAT EXCHANGERS Heinz Jacobs, Geldern, and Johannes Ciaesgens and Friedbert Heyn, Krefeld, Germany, assignors to Industrie-Companie, Krefeld, Germany Filed Sept. 1, 1955, Ser. N 553,170 6 Claims. (Cl. 257251) The present invention relates to improvements in or relating to heat exchangers, and is more particularly concerned with cast heat-exchanger tubes and heat exchangers assembled from such tubes.

Cast heat-exchanger tubes have the advantage, as compared with steel tubes, that they are resistant to corrosion and to short time excess temperatures, and that a large heating surface and consequently a high heat output can be provided with a small space. On the other hand, steel tubes have the advantage, as compared with cast heatexchanger tubes, that they can be welded without special preparations. The connection of the individual tubes to form parallel-flow tube blocks is facilitated considerably by welding, which also insures a nearly perfect fluidseal that is not possible to obtain to a similar perfection in the case of cast heat-exchanger tubes, which have hitherto required screw connections.

The object of the invention is to combine the advantages of cast tubes with those of steel tubes.

The invention consists in the provision of a cast-metal tube for use in a heat exchanger, said cast tube having a steel tube in the wall of at least one end thereof and prolongation of the cast tube, wherein the end-portion of the steel tube is fixed in the cast tube by casting the tube in such a way that said portion of the steel tube is embedded in the adjacent end of the cast tube.

The cast-in steel tube ends projecting from the cast tubes render possible the welding of the latter, so that the cast heat-exchanger tubes practically can be welded together to form parallel-flow tube blocks in the manner hitherto possible only with steel tubes.

A tight and durable connection between the steel tube and the cast tube is essential. For this reason it is advantageous if that end of the steel tube which is to be cast-in is sharpened in the manner of a knife-edge. The steel becomes reliably fused to the cast-iron at the knifeedge, thus formed, so that the union is and remains fluidtight. Alternatively, that part of the steel tube which is cast-in may be profiled so as to increase its surface. In addition, recesses may be formed in the cast-in part of the steel tube sections.

In order to obtain favorable conditions for the flow along the ribbed outer surfaces, it is advantageous to combine two tubes to form a single casting. Both tubes then have a common inlet and outlet aperture of a substantially oval cross-section. In such tubes, the shape of the cast-in steel tube may be adapted to the inlet and outlet cross-section of the double tube.

It is particularly advantageous to produce a whirling movement of the medium flowing through the tubes, because the heat exchange is thereby improved. In accordance with the invention, for this purpose, guiding fins in the form of a multi-thread helix are provided by casting on the inner surface of the tube wall, such guiding fins producing a whirling flow of the flowing medium and acting, in addition, as cooling fins in that they increase the inner surface of the tubes.

The said guiding fins may extend over the entire length of the cast tube, but they are preferably provided only at the ends of the tube and the cross-section of the cast tube within the guiding fins is preferably filled by an inserted member. The inserted member forces the flowing medium to flow through the passages between the guiding fins, so that a whirling motion is imparted thereto.

According to a further development, there are provided near to the ends of the exchanger tube supporting and screening flanges made in one piece with the cast tube. The said flanges protect the cast-in steel tube sections at the ends of the cast tubes and the welding joints thereof from over-heating by the heat-emitting gases which wash the tubes between the screening flanges.

In accordance with the invention, the gate in the upper section of the mould is advantageously disposed during the casting of the heat-exchanger tube right above the end of the steel tube which is to be cast-in. The poured stream of metal encounters this portion of the steel tube and heats it. It is thus possible to introduce the steel tube into the mould in the cold state, because it is heated by the poured stream of metal.

Instead of the outer steel tube ends being welded in tube plates in the assembly of the tubes to form heat exchangers, the cast-in steel tubes may be fashioned at their outer ends to polygonal flanges, the edges of which are welded to the edges of the flanges of adjacent tubes, so that the flanges themselves form the tube plate. It is further advantageous to bend over outwardly the edges of said flanges, with the result that the edges of said flanges abut at an acute angle and render possible the Welding of the edges by the simple melting-down method. When it is desired to replace a tube in the tube block, it can readily be detached from the tube block by grinding off the welding seam of the flanges of the tube concerned.

The elastic yielding connection of the tubes may be further improved by forming one or more constrictions between the flange and the cast-in end of the steel tube, so that the steel tube acts in the manner of a corrugated tube compensator. Such a steel tube having a flange and constrictions is advantageously assembled from two or more welded portions, the welding seams being placed at the narrowest points of the constrictions.

Further details of the invention will be apparent from the following description of the drawings, in which the invention is diagrammatically illustrated by way of example, and in which:

FIGURE 1 is a section through a cast tube end having a cast-in steel tube welded into an elastic steel plate;

FIGURE 1a is a section through another constructional form of the steel tube of FIGURE 1;

FIGURE 2 is a section through the end of a cast double tube and an adequate cast-in steel tube;

FIGURE 3 is a side-elevation corresponding to FIG- URE 2, partly in section;

FIGURE 4 shows an example of the supporting of the heat exchanger tubes in a vertical arrangement;

FIGURE 5 shows a tube block held together by an elastic clamp;

FIGURE 6 is a section through the end of a mould;

FIGURE 7 is a section through the end of cast tubes, having flange-like cast-in steel tubes;

FIGURE 8 is a side elevation corresponding to FIG- URE 7;

FIGURE 9 is a section corresponding to that of FIG- URE 7, showing steel tubes, having bent-over flanged edges, and

FIGURE 10 is a section corresponding to that of FIG URE 9, showing constrictions in the steel tubes adjacent the flanges.

The heat-exchanger tube 1 shown in FIGURE 1 has external fins 2 to improve the heat-transfer. Guiding fins 3 shaped as a multiple-screW-thread are provided on the inner surface of the tube 1. The medium, for example air, which enters the end of the tube is given a whirling motion by the guiding fins 3. Within the guiding fins 3, the cross-section of the tube may be filled by an inserted member 4, so that the air is forced to flow between the guiding fins (see FIGURES 2 and 3).

A short steel tube 5 is cast into the end of the tube 1. That portion of the steel tube 5 which extends into the cast tube 1 is provided with grooves 6 to produce an intimate connection between the steel and the casting. For this purpose, recesses 7 are also provided in the cast in portion of the steel tube 5.

In the constructional form illustrated in FIGURE 1a, the cast-in end of the steel tube 5 is sharpened like a knifeedge. In the casting, a fusion is reliably produced at the knife-edge 5, so that the connection is tight. Instead of segments of commercial seamless steel tubes, tubes of any desired shape, made of sheet metal sections, may be cast-in.

The outer end of the steel tube 5 is welded in a steel plate 9, forming the base of the exchanger. A type of connection hitherto impossible with cast tubes is thus produced. The steel plate 9 is thin, so that it is capable of yielding elastically under the varying thermal expansions of individual tubes. The steel plate at the other end of the heat exchanger may be thicker and consequently more rigid. In order to relieve the welding seams of the steel plate of mechanical stresses, the cast tubes are provided, near to their ends, with supporting flanges 10, thus supporting one tube against the other. In addition, the said flanges 10 protect the steel plate 9 and the cast-in steel tubes 5 from overheating by waste gases flowing in between the assembled heat-exchanger tubes 1 in the space between the flanges 10.

In the constructional form illustrated in FIGURES 2 and 3, two tubes are combined to form a double tube as a unitary casting. Consequently, the outlet aperture has a substantially oval form to which the cross-section of the cast-in steel tube 5 is adapted.

The cast heat-exchanger tubes may be assembled either in a horizontal position or in a vertical position. FIG- URE 4 indicates a proposed method of assembling the tubes vertically. It is essential to support the weight of the tubes in a way that the steel plate 9 forming the base is relieved of load. The supporting flanges 10 of the tubes rest between the steel tubes 5 on a metal grill or on intermediate metal elements 11 of a suitable shape which are disposed between the supporting flanges 10 and the steel plate 9. Further supports 12 can be provided below the supports 11 between the steel plate 9 and a supporting structure (not shown), for example, a supporting grill. The steel plate 9 and the welding seams 8 are thus completely relieved of load. The heat-exchanger block is preferably bound with metal clamps as illustrated in FIG- URE 5. The supporting flanges 10 of the tubes assembled to a block are elastically framed with a combination of angle segments 13, and, for example, of springs 14. When the flanges undergo thermal expansion, the clamping structure is capable of yielding.

FIGURE 6 shows the end of a casting mould in which the tubes according to the invention are poured. The steel tube 5 is inserted over a core '15 the Way that its profiled end extends into that part of the hollow exterior of the mould which forms the end of the cast tube. The gate 16 is disposed in the upper section 17 of the mould in such manner that the pouring stream encounters that end of the steel tube 5 which is to be cast-in. Thus, the steel tube 5 can be introduced into the mould Without being preheated, and the steel tube 5 is perfectly welded to the cast metal, e.g. cast steel or cast iron.

Instead of the steel tubes 5 being welded into a tube plate as illustrated in FIGURES 1 and 4, steel tubes 18 may be cast into the ends of the cast tubes, which are bent over to flanges at their outer ends (see FIGURES 7 to 10). The flanges 19 all have the same polygonal form and abut one another at their edges. The said flanges are welded together at these edges 20. The flanges 19 welded together thus form the tube-plate of the heat exchanger.

In the constructional form illustrated in FIGURE 9, the edges of the flanges 19 of the cast-in steel tubes are bent over outwardly. Consequently, the flange edges 21 of adjacent tubes abut one another at an acute angle. The edges can thus be simply welded together by the melting-down method.

The steel tubes illustrated in FIGURE 10 difler from those of the constructional form illustrated in FIGURE 9 in that a constriction '22 is formed between the cast-in end of the steel tube and that part thereof which is fashioned as a flange 19. The elasticity of such a steel tube end is considerably increased by one or more constrictions 22. This steel tube end is formed in two or more parts, the welding seams placed at the narrowest points of the constrictions between the individual parts.

We wish it to be understood that We do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to persons skilled in the art.

What we claim is as follows:

1. A heat exchanger comprising a plurality of elongate tubes supported in vertical position, each tube comprising a relatively thick-walled upper section of cast metal and a lower section of pre-formed steel integral with the upper section, each cast metal section having an external flange at its lower end abutting the flange of an adjacent tube, spaced vertically extending support means engaging said flanges to support the tubes and permit the lower sections of the tubes to depend the'rebetween, a generally horizontally extending and relatively thin steel tube plate supported by the support means at a Zone beneath said tube flanges, said tube plate encircling each tube lower section and being welded thereto, and said tube plate being sufflciently flexible to permit movement of individual tubes under thermal change.

2. A metallic heat exchanger comprising a plurality of vertically disposed tubes, each tube comprising a relatively thick-welled cast metal upper section and a relatively thin-walled steel lower section integrally united with and forming a prolongation of the upper section, each cast metal upper section having at its lower end a relatively heavy and radially extending external flange abutting the flange of an adjacent tube, a relatively thin steel tube plate disposed substantially horizontally beneath the flanges of said tubes, each tube lower section being projected through and welded to the tube plate, spaced vertically extending metal support elements engaging the top surface of the tube plate and the tube flanges, and vertically extending supplemental support means engaging the lower surface of the tube plate in alignment with the metal support elements whereby the tube plate and the welded joints with said lower sections are relieved of support load.

3. A metallic heat exchanger comprising a plurality of vertically disposed tubes, each tube comprising a relatively thick-walled cast metal upper section and a relatively thin-walled steel lower section, each tube lower section having its upper wall portion embedded in the lower wall portion of the upper section, each cast metal section having at its lower end a relatively heavy and radially extending external flange abutting the flange of an adjacent tube, a relatively thin steel tube plate extending generally horizontally beneath the flanges of said tubes, the tube plate being perforated at spaced points to receive the tube lower sections, said tube lower sections being projected through the tube plate and peripherally welded therewith, vertically extending metal support elements spaced between the tube lower sections engaging the top surface of the tube plate and the tube flanges, supplemental vertically extending support means engaging the tube plate lower surface directly beneath the metal support elements whereby the tube plates and the welded joints with the said lower sections are relieved of support load, and the tube plate being adapted to yield elastically in response to the varying thermal expansion of individual tubes.

4. The metallic heat exchanger as defined in claim 2 and wherein the metal support elements form part of a metal grill, and said elements engage the tube flanges at the abutting zone of adjacent flanges.

5. A heat exchanger comprising a plurality of elongate tubes, each tube comprising a relatively thick-walled intermediate section of cast metal and sections of preformed steel at each end of said section of cast metal, each of said sections of preformed steel being joined to its intermediate section by casting molten metal around a part of said section of preformed steel which part extends into said intermediate section to form said tube, said cast metal section having an external flange adjacent each end thereof abutting the flanges of adjacent tubes and forming with said flanges two closed Walls near the ends of the cast metal sections protecting the preformed steel sections from hot gases of the exchanger, generally radially extending plate means encircling each of the preformed steel sections and integrally joined therewith, and the plate means being flexible between adjacent tubes to permit longitudinal movement of individual tubes under thermal change.

6. A heat exchanger comprising a plurality of elongate tubes, each tube comprising a relatively thick-walled section of cast metal and sections of preformed steel at each end of said section of cast metal, each of said sections of preformed steel being joined to its intermediate section by casting molten metal around a part of said section of preformed steel which part extends into said intermediate section to form said tube, said cast metal intermediate section having an external flange adjacent each end thereof abutting the flanges of adjacent tubes and forming with said flanges two closed walls near the ends of the cast metal sections protecting the preformed steel sections from hot gases of the exchanger, plate means forming a second wall at each end of said tubes, said plate means being spaced longitudinally outwardly of the wall formed by said flanges, each preformed steel section being projected through the plate means and integrally joined therewith, and the plate means being flexible between adjacent tubes to permit longitudinal movement of individual tubes under thermal change.

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